An engine charged with a turbocharger comprising a multi-channel turbine includes a wall which separates the channels to an extent to the rotor to vary the interaction between the two channels. A dual flow turbine is able to separate two flows of two cylinder exhaust groups, which helps to improve low end torque. The efficiency and the separation characteristic of dual flow turbines are influenced by the spacing distance between the tongue of the turbine housing wall and the turbine wheel. The engine may consider different spacing characteristics of the turbine in different operating conditions to increase efficiency.
One approach is to provide a wall which separates the channels from one another to the rotor, at low engine speeds/loads this aids in pulse charging. Another approach is to provide a wall which leaves spacing to the rotor, thereby providing a degree of interaction between the two channels, at high engine speeds/load this aids in constant pressure charging.
A potential issue noted by the inventors with the above approaches is that providing a wall which has a fixed position only enables the engine to be optimized under certain operating conditions.
One potential approach to at least partially address some of the above issues includes a charged internal combustion engine comprising at least one cylinder head with at least two cylinders and at least one exhaust-gas turbocharger with at least one turbine. Each cylinder of the charged internal combustion engine comprises at least one outlet opening for discharging the exhaust gases out of the cylinder with each outlet opening being adjoined by an exhaust line. The at least two cylinders are configured in such a way as to form at least two groups with in each case at least one cylinder. The exhaust lines of the cylinders of each cylinder group merge to form a respective overall exhaust line, thus forming an exhaust manifold with the at least two overall exhaust lines being connected to a multi-channel segmented turbine. The turbine comprises at least one rotor mounted on a rotatable shaft in a turbine housing and the at least two channels of the turbine, when viewed in a section perpendicular to the shaft of the rotor are arranged one on top of the other at least along an arc-shaped section and enclose the at least one rotor in spiral form at different radii and are open toward the at least one rotor in each case along a circular-arc-shaped segment, in such a way that in each case one overall exhaust line is connected to one of the at least two channels of the turbine. In each case, the two adjacent channels are separated from one another, at least in sections and in a continuation of the overall exhaust lines in the turbine housing by means of a housing wall. At the rotor side, the at least one housing wall that separates two adjacent channels has a free tongue-like end and ends with a spacing to the at least one rotor, such that a tongue spacing is formed. Here, the multi-channel segmented turbine is the turbine of the at least one exhaust-gas turbocharger wherein a movable annular support is provided which has at least one tongue-like element and which is displaceable in translational fashion along the rotatable shaft for the purpose of varying the tongue spacing. When the support is in a first working position, the at least one tongue-like element lengthens the free tongue-like end of the housing wall that separates two adjacent channels such that the tongue spacing is reduced to the at least one rotor. When the support is in a rest position, the at least one tongue-like element is positioned laterally adjacent to the at least one rotor.
In this way, a multi-channel turbocharger with adjustable tongue spacing may vary the degree of interaction between the channels via the tongue spacing. Thus, a flow transfer duct may be opened or closed based on engine operating parameters to change the degree of separation of the channels to the rotor and better enable operating at different conditions. For example, at high engine loads and/or speeds, when a large exhaust gas volume may be present in the exhaust manifold, the degree of interaction between the channels may be high by adjusting the annular support to open a flow transfer duct. In another example, at a low engine load, when a small exhaust gas volume is present, the tongue spacing may be lengthened by adjusting the annular support to close a flow transfer duct and increase the degree of separation of the channels.
In another example, a method for operating a charged engine, comprises displacing an annular support with at least one tongue-like element in a translational fashion along a rotatable shaft of a turbine from a rest position to a first working position in order to increase a degree of separation of at least two channels of the turbine by reducing a tongue spacing. In this way, by reducing the tongue spacing, it is possible to decrease the degree of interaction of the two channels to the turbine under engine operating conditions where a difference in exhaust flow in the two channels may exist. Thus, mutual influencing of the pressure pulses of the exhaust flow may be substantially reduced and turbine efficiency increased.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.